Dynamic Response of Frozen Pisha Sandstone Reconstituted Soil under Multi-Stage Cyclic Loading

The dynamic mechanical properties of basic fill soil in seasonally frozen regions are highly sensitive to temperature. This study investigates the dynamic behavior of a widely used fill material in the Loess Plateau Pisha Sandstone (PS) regions, namely, Pisha Sandstone Reconstituted Soil (PSRS), under multi-stage cyclic loading. A series of cyclic triaxial tests were conducted on PSRS under different temperatures (0, −5, −10, −15°C), confining pressures (100, 200, 300 kPa), and loading frequencies (1, 2, 5 Hz). The results indicate that the dynamic elastic modulus (DEM) exhibits three stages of variation: an initial elastic stage (with DEM remaining stable), an elastoplastic stage (DEM gradually increasing), and a failure stage (DEM rapidly decreasing). The maximum dynamic elastic modulus (DEM max ) increases rapidly as temperature decreases. When the temperature is constant, DEM max is positively correlated with both the confining pressure level and the vibration frequency. During the non-failure loading stage, the damping ratio at 0°C first decays rapidly and then stabilizes slowly, whereas at −5°C to −15°C, it shows a pattern of rapid initial decay followed by stabilization. During the failure loading stage, the damping ratio of all temperature groups exhibits abrupt increases, but lower temperatures significantly delay the occurrence of the critical failure point. This study established a DEM max prediction model for frozen PSRS based on the coupled effects of temperature, confining pressure, and frequency, with R 2 = 0.858 and mean absolute percentage error ≤ 7.73%. This model provides a practical theoretical framework and a reliable tool for predicting PSRS stiffness, which can guide the design and stability assessment of transportation infrastructure in cold regions.